Fluid Flow in Spirally Vortex Structures. Notes on Bird Flight

The research paper explores the nature of fluid-mechanical vortex coils, which consist of spirally arranged coherent vortex filaments. It highlights the lack of a universally accepted theory regarding spiral vortex formations in fluid mechanics, despite the historical contributions from figures like Helmholtz. The paper discusses modern theoretical approaches that define coherent vortex formations as connected areas exhibiting dominant vortex strength, emphasizing the significance of these structures in understanding fluid dynamics.